Refining pressure distillates



Jan. 1, 195o. E F ENGELKE REFINING PRESSURE DISTILLATES Filed April 28, 1951 Patented Jan. v1, 1935 Doherty `c(irpeffattionlof Delaware ,"Applfitation*Abdias, 1931, seriainofsaasss" "Search Company,

` ,This invention relates toa process for refining pressure :distillates and:morel,particularly toa process for refining` crackedggasolinesfto purify the same with respectto gum and color-forming L constituents.

YAnti-knock motor'fuels are "produced a` large scale: by cracking petroleum oils at high temperature (850 to 1050D F.) by which large4 amounts of olenhydrocarb'onsas Well as aromatic hydrof lcarbons are formedlfj As is "well known gasolines u lproduced in this:marmerhave a greatgtendency to turn a deep `yellow color and to` deposit gum. Furthermore such gasolines cannot be refined by the usual sulphuric acid method `,without considerable loss both in the quantity of the fuel and in,` antiz-knockproperties. Attempts have been -made to refine cracked gasolines by passing them in' vapor form through a bed of adsorptive clay 3v 'appended claimaf l AllTheviigureV `of the such as fullers` earth,` but this treatment is too severe, and doesnot prevent trouble-from gum, particularly with `gasolines produced by high temperature cracking. i y I 1 Accordingly, the primary object of the present invention is to provide a proces'srior` refining high i temperature `cracked gasolines without causing a substantialpreduction'lin their anti-knock value and which will at the same time'produce a color` land gumstable gasoline. i

parent from the,V following description i andv `the drawing is 4a. diagrammatic `representation or llow* sheet4` of l the process aocording` to the present invention. i u "According to the process of thepresent invention', the pressure distillate orcracked gasolineV to be stabilizedas to color and gum formation is washed infan agitator chamber 2,with` an alkali "solution such as caustic sodasolution, and is then directed by means of apump 4 to a second agitator chamber', where it, is treated with'a sweeten- 'ing agent such as sodium plumbite solution and with a slight amount of elemental sulfur to break the suspension of any lead compounds formed. The sweetened gasoline leaving'the agitatorl may betdirected by means `of a pump Sinto a iiltering chamber `10, Where it'istreated with-a -iiltering medium such as iullers earth if desired; and is then conducted to a; charge tank 12. y@ If `the process is operated continuouslyg with a continuouscharge of pressuredistillate, `the operation of the process will `beas above `described,

l butif the processis to `berun'in batch,v return lines to both: the agitatorst2and`6 are provided for the return and retreatmentof the treated gasoline leaving the agitators. -`Furthermore a by-pass line is provided to permit the sweetened gasoline leaving the agitatorchamber to berun directly to the charge tank'1v2 without passing through the 'filtering chamber 10.

sulphurous gases.

1 Further` objects and advantageswilllbefapi `FromI the tank172, `thesweetenedand iiltered distillate is conducted by means of a pump `14:

either to a'heater 1,6 andthence to atreating still 13, 01 directly to the jtreatingfstill Without first Dassingthrough the'heater.` i l l l An un'saturatedhydrocarbon gas which is obtainedas a byproduct froma cracking stillduring apetroleum crackingiprocessV and which has beenwashed with alkali to remove the sulphurous f compounds therein, isV conducted 'bymeans of a pump `through a gas purifier 22 and to heater 16 where it is mixed with the sweetened and filf tered gasoline entering the heater. In thegas purier22 both the cracking still gas entering the `system and the recirculatedv gas may be treatsuch as activated carbon, or a liquid contact purifyingmedium such as caustic soda solution so as to wash such cracking still gas Vfree of entrained The ltemperature "of the mixture of cracking still gasand sweetened gasoline is raised in the heater 16 to that necessary `to vaporize the gasoline and the mixture orvapor and gas is` then conducted to the treating stil118.` Ifthe sweet-r ened gasoline has not been run through the `heater 16,;but hasbeen conducted` directly Ito the `treating still 18, `it will be` mixed with the gas leaving `the heater prior to: enteringthe treating still, the temperaturl'e,iofffthel;cracking fstill' gas under` these circumstances-being raised dri the `heater 16to tabout 34N-400"` F., and the gasoline Willbe completely vaporizedy on contact with the `hot gas,the mixture of vapor and gas being `conducted;` as before into the treating still 18, 1.. f

, ed by either `a solid contact purifying medium In the treating still 18,v Whichisin the form of a bubbler cap column, the temperature vof the and thence either returned forretreatment in the heater 16 in Aadmixture with, the purified cracking still gas or returned to the cracking unit. The low boiling fractionsof `the pressure distiltreatment will, be .regulated Lby late being treated inthe treating stilli18, which fractions are` maintained constantlyin thevai por phaseand in admixture with the cracking stillgas, arepassed upwardly througha series of trays of 4bubbler `caps28 and abed of oxidizing material 30 and thence fromthe treating still to acondenser 32. From the condenser 32, the condensed gasoline andthe gas are conducted toa separating tank 34, whence the gas-free stabilized gasoline is obtained and the cracking still gas which is separated from the gasoline is conducted to thegas purifier 22, and again returned #for radmixture with a` freshcharge of gasoline "1GO `undergo treatment intheiprocess, AThe temcracked gasoline or pressure distillate it vliasbeeer'i' found to be beneficial for the treatment of a" perature Within the .treating still 18 and return of the heavy ends from tank 26 through heater 16 to the treating-still 18 are controlled sol as to give inseparatilg tank-34 agasoline of the desiredend point. The stabilized gasoline leaving y thc-:separating tank 34may be resweetened with a sweetening agent such as sodium plumbite so- 1uticn with a slight amount offeieirieiitai sulfur to break any suspension` of lead.. compoundsy formel1 y;

While the-above-described process has been herein directed toward the treatment solely of a blendtliuslprodueedf Blends'prodi'iced Vin this manner halve "pfrofvedf to be much more highly 'stabilized thaneither component of-'the' blend. the' blendup'on b'eingrsubjecte'd to the action of 'strong light forA acorisidereme pericdof time showing no lossf'in` color' and no' formation of gum.. l f The' sweeter'iing agent used according tothe present invention either' lbefore tliedistillation treatment orl subsequent' to the' distillation` and condensation of thel cracked gasoline alone or of the blend of cracked gasoline and straight rilgasli, maybe a* s'odir'iiplunibite soltiori with a slight amount of elemental sulfurY added.- Aitamiiwhiaealf copper oxide (or sulfate) solution nas' also' beenfondf to be excene'nt sweet-- ening agent and may be used place of thes'od ium plumbitesolution and-elemental sulfur in any fthe va'v'e-S'vveete'lfliig or` rsweet'enlrig ff Y'rifle bedof 'oxidizing material 30 is composed oi`= a siiper'oxide'l ofa heavy metal-such as Mnz or Poot whicr'tactsftcoxidize any sinfurous mang the vapors' being treated in and aisoaids iii the stabilizay distillate. if, afteiaperiod ot Y useethese. superoxi'des require regeneration; sueiiewregeneiaticn ci the superoxides be effeet'edi during. the peration of the 'process by introducing air-" iritothftleating still l18 atthe zone croxidationf. f The heat Within'- the still promotes' the combination" of tliefostygeniof the air with the sulfur held Within thelzone of oxidationto'forni Sulfurol'i's' compounds, the oxygen of the'air replace 'ing'thesulfur ofthe" sulphide compounds of the' f' heavy metals formed.

- Vill/lille the pif'ocessVA a" brding to the present in' volition-has been'. described in connection with the'treatmentfofipressure distillate or 'cracked gasoline Withan--alkali Wash,` 'a sweetening agent,

- and'failtering material prior to the distillation inv admiXtuie with a cracking still gas, it is to be notedthat any or all of these steps may be omitted if such a; course is considered to be advantageous under specific conditions. It has been found that some gasolines do' not require a` preliminary sweetening and in such eases ay Vpreliminary sweetening may be omitted.

tThe process vac'z'ccirding to the present invention Willa'be found to be of considerable advantage in stabilizing'v a.v cracked gasoline or a blend of cracked gasoline andstraight' vrun gasoline as to color and formationv While the treated gasQe line still retains its high anti-knock value. In Inost cases the material which has been treated according: to the process described'herein will remain stable for a` periodtofptvvo yearsior more without an appreciable change in color or the yslightest formation of gum and will retain its Value as an anti-knock motor fuel. In certain cases hovvever',`tvhere a slight precipitation is noticed yafter anfextended period of storage the precipitate-'Will befound to be in the form of a liquid;lv and ,aSfSllch has no harmful effect in the motor fuel. No 4solid or sticky gum is formed.

Fro'rif various'fte'sts that have been made it wouldv Aappear that the free hydrogen or unsaturated hydrocarbon content of the cracking still g'as reacts"y with the unstable constituents of the` pressure distillate .to :form a gasoline' that'is stable' with respect to color` change' and gum' formation. VWhile the best results have been ob.-vv tained from the use of gas from a crackingy still; favorablel results' 'have also'been` obtained from the'use ofv other hydrocarbon; gases containing free'y hydrogen or-,unsatur'atedconstituents.

Having described the'invention inits preferred formi what i`s` claimedlasnevv'is:

1. In the process of:refining!pressure distillate,` Without substantially reducingv its anti-'knock value Vby the use ofconcentrated acid, for tlie purpose of sweetening tliedistillate and render'- i'ng' gum stable,l the steps "which consists'in sweetening the distillate by passing it inl intimate Contact with an alkaline sweetening agent, frac= tionall'y distilling the resulting' sweetened fdis'e' tilllate WhileI maintain-ing it inintirn'ate contact Witli al cracked hydrocarbon gassubstan'tially free of 'sulphur' compounds', and'caiirying out? said fractional distillation at a temperature'notsub-i statially exceeding 400 F1 2:11 The' process deiiiied by claim 1 in whicntlie rackd hydoo'arborigas' 'used in the distilling operatic 'is passedlin a' vclosed cycle whichvrine ellfds'ai-spifyingzoe. I f

3. In the process of reiinirigpressure distillate, without substantially' reducing its anti-'knock value by the use 'of concentrated acid, for':the purpose of svveeteningl the distillate' andrendere' -irigit' gum@ stable, the" st'ep'swhich' consistin blend-ing a pressure'distillate'with a; straight run gasoline distillate, sweetening.. the resulting blerd'edi clis'tilltte'al fractionally vdistilling Athe svl'r'e'eter'ied` blend the presencey of .andin intimate contact With a' purified cracking still'igas' substantially free' of sulphur' compounds; and carrying out'said fractional distillation ata terne' perature not substantially exceeding 400 F'.l

4. The process" defined by claim 3 in Whichthe cracking still gas used in the distilling operation is passed in a closed cycle which includes a gas purifying zone.

5. In'the process of refining pressure distillate, Without substantially reducing its. anti-knock value bythe use of concentrated acid, for the purpose of svveet'ening the distillate and render' ing it gum stable, thesteps which consist in" blendinglapressure distillate with a straight run gasoline'and subjecting the blend thus produced to the action of an alkali solutionand a plumbite solution;V fractionally distilling the sweetened blend in the presence of cracking still gas at a temperature not substantially exceeding 400 F., and passing the vaporsof distillation througha inass of oxidizing material comprising a supere' oxide of a heavy metal.

' .ERNESTy mfENG-ELKEL.: 

